Folks, if you don't think Iran has made nuclear weapons, and is fully-capable of detonating at least a crude one at this point, you're nuts.

Additionally, if you think their intent is not to have dual-use nuclear technology you're dumber than a box of rocks.  And unfortunately, most of America is dumber than a box of rocks when it comes to this subject, and you've been intentionally kept dumb.

I'll attempt education here -- and urge you to fact-check all of what I have to say.  Draw your own conclusions from that point, but don't be a lemming on this -- it's important.

America and indeed most of the world think of nuclear power in terms of uranium and plutonium fueled water (or liquid sodium) cooled reactors.  The former are used to make power, the latter are used for formal "breeding" of fuel.  The US nuclear industry attempted to run a liquid sodium power reactor at Fermi I in Monroe MI but the attempt nearly ended in disaster when it melted down (due to some foolish cost-related issues that had nothing to do with the viability of the basic design -- it's solid.)

We think of nuclear power this way because it's all we've seen in the public eye.  Power reactors typically have about 5% fissile material in the fuel.  The rest is other things, mostly U-238, a non-fissile material, and various binders and other other materials to make an oxide-based fuel that is essentially a ceramic.

This is very inefficient way to burn nuclear fuel.  Since the fuel contains only 5% fissile material only about 5% of it is consumed.  The rest is bombarded and, over time, turns into other things.  Some of them are very high-level radioactive waste products that are dangerous for thousands or even tens of thousands of years.

But one of the things that U-238 turns into is Plutonium.

Plutonium is an excellent bomb-making material, as is highly-enriched uranium.  It is difficult to separate enough fissile uranium to make a bomb, because it is chemically the same as the sort of uranium that won't detonate.  But plutonium is a different matter -- it can be chemically separated and thus is much easier to extract.

In addition traditional water-cooled reactors have a lot of engineering issues.  Water is not a particularly friendly thing to use for coolant at high temperatures, because it has to be kept under enormous pressure or it instantly flash-boils to steam.  The essential purpose of using water in a reactor is not only for cooling but to moderate the reaction -- fast neutrons are very inefficient at causing fission, so you need to slow them down.  The water does that, in combination with carefully-engineered arrangements of the fuel so the distance the neutrons travels in the water is likely to produce the desired energy when the next impact takes place.  But if you lose the ability to remove the heat in the water fast enough, say through a loss of power, or if the integrity of the pipes is lost then you have an instant disaster on your hands as the fuel will melt without coolant, as happened in Fukushima.

Now all of this would be just a nasty coincidence -- that is, that producing power always came with proliferation risk for nuclear weapons and risks of meltdown and similar engineering problems -- if it was true that there was only one viable nuclear fuel cycle.

The problem is that there is in fact another viable nuclear fuel cycle.  Thorium.

Thorium itself is not fissile; it is fertile.  What that means is that when you bombard thorium with neutrons it becomes a fissile element - in this case, the isotope of uranium 233.

This fuel cycle has several characteristics that are very different from the one we have dotting our landscape for power production both here and abroad:

• It is very efficient on a comparative basis.  That is, a relatively-large percentage of the time a thorium atom's product (U-233) captures a neutron it turns into fuel as opposed to toxic radioactive waste.   The result is much shorter-lived radioactive waste products.
  
  
• The actual fuel is undesirable compared to U-235 for nuclear weapons.  U-233 has a habit of "fizzing", or going off "too quickly" when put into a bomb.  This can be overcome but it's difficult (and thus it's simply easier if you want bombs to use either U-235 or plutonium.)
  
  
• This fuel cycle produces relatively small amounts of excess fuel. That is, it "breeds" at a rate that exceeds the fuel used to start up the reactor, but not by a huge amount.  This too makes it more difficult to use such a fuel cycle for weapons, since you need a lot of reactors to make a few bombs, as opposed to a few reactors to make a lot of bombs.
  
  
• The fuel it produces is contaminated with U-232.  This is a very undesirable contaminant as it has a relatively short half-life and emits very high-energy gamma rays along its decay chain.  As such in order to use the product for weapons you have to remove this isotope in heavily-shielded facilities through isotopic separation or you bomb kills anyone who tries to work on it (such as, for example, to mount it on a missile or load it in a plane.)  Isotopic separation is what Iran (and others) are doing now with centrifuges but unlike with U-235 separation you can't allow anyone near the equipment due to the gamma emissions, which makes maintenance and operation a royal bitch.  It's much simpler to just separate out U-235 from natural ore if you want bombs.  But U-232 is just fine inside the reactor.
  
  
• We can run such a reactor with a liquid salt as both coolant and carrier for the dissolved fuel, having the moderator fixed in the reaction vessel, instead of using water as a coolant and moderator.  This has a number of advantages, with one of the biggest ones being that you don't need high-pressure systems any more and the meltdown risk disappears. It also operates at a higher temperature, which is good for thermodynamic efficiency. This is not a panacea as there are material engineering challenges to liquid-salt designs, but we proved that this basic design works -- and is intrinsically safe -- during the 1950s and 60s at Oak Ridge with an operating unit.

So what's going on here, in total?

Simple: Since the 1960s there has been little to no legitimate argument for using a uranium-plutonium fuel cycle for nuclear power production unless you want dual use.

Yes, that includes here, that includes Japan, that includes Europe, and.... it includes Iran.

Iran wants at least the ability to produce bombs, if it doesn't already have them, just like everyone else who has pursued nuclear technologies.

All these nations want "nuclear energy", in point of fact -- both of the sort that releases that energy nice and slow for power production, and of the sort that releases it very rapidly for extremely destructive use.

And that's a fact.